The Study Of Functional MR Imaging In Assessing Lumbar Interveterbral Disc Degeneration In Patients With Low Back Pain

Objective: To assess the diagnostic value of3.0T functional MR imagingsuch as DWI, DTI and T2^*mapping for early degeneration of lumbarintervertebral discs. To improve the accuracy in diagnosing degenerationlesions of lumbar intervertebral discs, various degeneration features wereobserved on functional MR imaging in patients with low back pain. Thediagnosis value of functional MR imaging was analyzed, and the associationbetween MR sequences and clinical data was evaluated in patients with lowback pain.Materials and methods: The informed consent was signed by allparticipants before the examination. Exclusion criteria including: followingpatients were excluded through the interrogation and necessary auxiliaryexaminations （such as laboratory examination）: lumbar traumatic compressionfracture, lumbar vertebral tumors, infectious disease, deformity and otherdiseases. MRI image artifacts observed or measured.1Study object:（1）60patients complained of low back pain wererecruited, including male in26cases and female in34cases, age range19-66years, average42years old. Low back pain was chief complaint for allpatients. Medical history was last from3months to10years.67volunteerswere severed as control group, including male in33cases and female in34cases, age range19-65years old, whose average34.3±13.1years. The casegroup and control group were examined by routine MR and MRdiffusion-weighted imaging.（2）21cases underwent DTI scanning and FAvalues of intervertebral disc were obtained.12cases of them underwentT2-STAR MR scanning and get T2^*values.2Examination methods: Lumbar examinations of conventional MRIroutine, DWI, DTI and T2^*mapping sequences were performed on participants using Siemens3.0T Verio MR system. MR parameter: sagittalTSE T2WI sequence （TR/TE=4000ms/42ms）, slice thickness,4mm; FOV,300mm×300mm. Fat suppression technique were used. DWI: SE-EPIsequence （TR/TE=5842ms/83ms）. matrix,164×164, FOV,281mm×281mm,lice thickness,3mm. Diffusion gradient factor b value is set to0,800s/mm²,diffusion direction3, bandwidth of1644HZ/Px.（2） T2^*and DTI study of thescan. Sagittal T2^*mapping （TR/TEs=1200ms/13.8ms,27.6ms,41.4ms,55.2ms,69.0ms）, slice thickness of4mm;300mm×300mm FOV; DTIsequence select single-shot echo planar diffusion tensor imaging （EPI） insagittal plane （TR/TE=3300ms/72ms）. Matrix128×128,300mm×300mm FOV,TR3300ms, TEs13.8ms,27.6ms,41.4ms,55.2ms,69.0ms, slice thickness2mm. b value is set to0,300s/mm², diffusion direction12, bandwidth of1502HZ/Px.3Observation date: ADC value, FA value and T2^*value of lumbarintervertebral discs were measured at the sagittal middle slice. RoundROI（region of interest） was used, including the nucleus area, outcluding theendplate and cerebrospinal fluid. ROI size was5pixels, Each disc of the casegroup and control group were classified according to Pfirrmann standard[1].3.1Index of clinical observationVisual analogue scale （VAS） of pain, VAS standard:0points-10.0points:painless;0-3points: mild pain, patients can tolerate;4points-6points: Thepain effect the patient’s sleep;7points-10points: patients have graduallyintense pain. Three groups were divided according to VAS, mild pain:1-3;moderate pain:4-6; severe pain:7-10.3.2Indexes of imagesLumbar intervertebral discs of127cases （60patients and67volunteers）were classified using Pfirrmann standard by two doctorsThe â…  to â…¤g rade were given1points-5points accordingly.4Data analyze:4.1All participants were divided into4groups according to the clinicalVAS, namely asymptomatic group, mild pain group, moderate pain group, severe pain group. The ADC values were compared among4groups. Thedifferences in ADC values between the case group and control group wereevaluated. The ADC values of the intervertebral disc were comparedaccording to different Pfirrmann grading level. The ADC values of theintervertebral disc were compared according to different segments betweencase group and control group.4.2To evaluate the value of the functional MR imaging and thecorrelation between of the intervertebral disc and Pfirrmann grading bymeasuring the ADC value, FA value and T2^*value.5Statistical analyze: ADC value, FA value and T2^*value which weremeasured by two doctors were analyzed using ICC; The result of Pirrmanngrading was undergone Kappa consistency test.5.1ADC value and Pirrmann grading were analyzed:（1） mean ADCvalues of the case group and the control group were compared using twoindependent samples T test or two sample rank sum test.（2） ADC value indifferent section of lumbar was compared between the case group and controlgroup using two independent samples T test or two sample rank sum test.（3）Pirrmann classification of case group and control group were compared withchi-square test.（4） ADC values of intervertebral disc in different levels werecompared with multiple sample comparison ANOVA or nonparametricmulti-sample comparison test. LSD test was used to compare the differenceeach other.（5） ADC values of4groups divided by VAS were compared withmultiple sample comparison ANOVA or nonparametric multi-samplecomparison test.5.2The correlation among ADC value, FA value, T2^*value andPfirrmann classification results of intervertebral disc were analyzed with thePearson or Spearman test.Results: ADC values were analyzed using effectiveness analysis, theresults for ICC （single） was0.897, ICC （average） was0.946; For FA values:ICC （single） was0.988, ICC （average） was0.994; For T2^*values: ICC （single）was0.987, ICC （average） was0.993. The results indicate two doctors data have a good consistency. Classification result of two doctors obtained goodconsistency with Kappa value0.982. Conclusion was used for inconsistentcases, and served as final data.1ADC value of the case group is （1.56±0.38）×10^-3mm²/s, ADC value ofthe control group is （1.62±0.39）×10^-3mm²/s, two group P value is less than0.05, that illustrate two groups had significant difference, namely comparedwith the control group, ADC values of the case group was small than that ofthe control group. ADC value of two groups have obvious difference in L3-4and L1-2, and there was no significant difference in other intervertebral disc.2The ADC values of different clinical symptoms groups show significantdifference, with value0.002. The ADC values showed a decreasing trend, longwith pain level increased. For ADC values, there was no significant differencebetween the control group and the mild pain group, no significance differencebetween moderate and severe pain group, Significant differences were foundbetween control group and mild pain groups versus moderate and severe paingroups respectively.3There ADC values show obvious differences among different Pfirrmannlevels of intervertebral discs, the ADC values of degenerative intervertebraldisc were lower than that of the normal intervertebral disc. The ADC value ofthe different levels of intervertebral disc had significant difference. The ADCvalues of different classification had significant difference, exceptgradeâ…  andâ…¡ i ntervertebral discs. The ADC values of L4-L5and L5-S1discswere relatively higher than that of L1-3discs.4Significant correlations were found among ADC values, FA values, T2^*values, and classification results with P values less than0.05.Conclusions:Lumbar interveterbral disc degeneration was one of the reasons for lowback pain. ADC value, FA value and T2^*value could make a quantitativeevaluation for interveterbral disc degeneration to a certain extent.